Budget summary
Total draw
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Available
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Headroom remaining
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Utilisation
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PoE Budget Calculator
Plan Power-over-Ethernet loads against your switch budget. Add devices by IEEE 802.3 PD class, see total draw, headroom and over-subscription warnings.
1. Switch PoE budget
2. Connected devices
Add each connected device group. PD class drives PSE-side per-port allocation (IEEE 802.3af / at / bt).
3. Result
IEEE 802.3 PD class reference
| Class | Standard | Max at PD (W) | PSE-side per-port (W) | Typical use |
|---|---|---|---|---|
| 0 | 802.3af | 12.95 | 15.4 | Default, VoIP phones, basic IP cams |
| 1 | 802.3af | 3.84 | 4.0 | Low-power sensors, micro APs |
| 2 | 802.3af | 6.49 | 7.0 | Mid-range VoIP, low-power IP cams |
| 3 | 802.3af | 12.95 | 15.4 | Standard PoE; older WAPs, PTZ cams |
| 4 | 802.3at (PoE+) | 25.5 | 30 | WiFi 5/6 APs, larger PTZ cams |
| 5 | 802.3bt Type 3 | 40 | 45 | WiFi 6E/7 APs, video phones, kiosks |
| 6 | 802.3bt Type 3 | 51 | 60 | High-density APs, thin clients |
| 7 | 802.3bt Type 4 | 62 | 75 | LED panels, digital signage |
| 8 | 802.3bt Type 4 | 71.3 | 90 | Pan-tilt PTZ with heaters, small access controllers |
PSE-side numbers include cable loss reserve per IEEE. Always size your switch against PSE-side, not PD-side.
When the budget is tight
- Split across switches. If headroom drops below 10%, move high-draw devices (Class 5-8) to a second PoE switch rather than running on the edge.
- Stagger boot order. Some switches let you prioritise ports so management VLAN devices boot first if total demand exceeds budget.
- Mind the upstream supply. 740W of PoE budget means the switch needs to draw ~800W from mains; check your UPS and breaker capacity.
- Cable matters. Class 5-8 require Cat5e or better with all 4 pairs intact; old shared-pair patch panels won't carry 90W reliably.
How to use the poe budget calculator
- Enter the total PoE budget your switch advertises in watts. Use a preset for common switch families if it matches.
- Add each connected device group (VoIP phones, access points, cameras) with its IEEE PD class and how many of that type you have.
- Click Calculate budget. The tool sums PSE-side per-port allocation, subtracts your headroom reserve, and shows whether you fit, are tight, or oversubscribed.
Frequently asked questions
How is PoE Class different from total PoE budget?
PD class is per-device — IEEE assigns each Powered Device a class 0 through 8, which fixes its maximum draw. Switch budget is the total wattage the switch can deliver across all PoE ports combined. A switch can have, say, 24 PoE+ ports rated at 30 W each yet only a 195 W total budget — meaning you cannot run 24 access points at full draw simultaneously.
What is the difference between PoE, PoE+, and PoE++?
PoE (IEEE 802.3af) delivers up to 15.4 W per port, enough for VoIP phones and basic cameras. PoE+ (802.3at) extends that to 30 W for Wi-Fi 5/6 access points and PTZ cameras. PoE++ (802.3bt Type 3 and Type 4) reaches 60 W and 90 W per port, supporting Wi-Fi 6E/7 APs, LED panels and small access controllers.
Why do I need more headroom than just the sum of device wattages?
Devices rarely sit at peak draw, but they can spike together at boot or during PoE renegotiation. Switches also burn a small overhead for management and PoE controller. A 20% headroom reserve gives you margin for those spikes plus space to add new endpoints later without re-cabling.
Can a Cat5e cable carry 90W PoE++?
Yes if all four pairs are intact and the run is under 100 metres, but it is on the edge of spec. Cat6 is safer for Class 7 and 8 because lower DC resistance means less heat in the cable bundle. Old shared-pair patch panels and connectors rated only for fast Ethernet will not survive 90 W reliably.